1. Field of the Invention
This invention relates to a camera having a focal plane shutter. More particularly, it relates to a camera body housing a focal plane shutter.
2. Description of the Prior Art
A recent demand for a lighter-weight and lower-priced camera has been making it necessary to develop a lighter-weight and lower-priced shutter. There has been proposed a shutter plate made of a plastic material, as described in Japanese Utility Model Application No. 138990/1986 filed by the assignee of the present application. A camera body which is made of a plastic material is already commercially available. This camera body has, however, a greater wall thickness than that of a metal body, so that it may make up for the lower mechanical strength of the plastic material. This increase in wall thickness of the camera body tends to result in a larger camera, contrary to the demand for a smaller camera. This problem is particularly noticeable with a camera of the type having a body in which a shutter of the unitary construction is incorporated. An increase in distance between the film plane and the shutter plane is very likely to bring about a reduction in shutter efficiency and thereby the lack of uniformity in exposure.
Reference is now made to FIGS. 4 and 5 showing a conventionally known structure by way of example. A camera body 10 has a central aperture 11 and defines a housing 12 for a film magazine on one side of the aperture 11 and a housing 13 for a takeup spool on the other side thereof. The camera body 10 is also provided above the aperture 11 with a plurality of threaded holes 14 for receiving screws 36 for securing a shutter assembly 30 to the camera body 10. The shutter assembly 30 includes a base plate 33 having a central opening 33a and a holding plate 34 positioned behind the base plate 33. The base plate 33 and the .cover plate 34 are spaced apart from each other and define therebetween a space in which a plurality of shutter blades are provided. The base plate 33 is provided along one vertical edge thereof with a mechanism 35 for moving the shutter blades for film exposure. The shutter is of the type which is well known in the art, as disclosed, for example, in Japanese Utility Model Application No. 138990/1986, and no further description will, therefore, be made of the specific construction of the shutter per se. The base plate 33 is provided with a plurality of lugs 33b projecting from its upper edge. Each lug 33b has a hole 33c which is aligned with one of the threaded holes 14 in the camera body 10, so that each screw 36 may be passed through one of the holes 33c into the corresponding hole 14.
The body 10 is provided on its rear surface with a plurality of film guide rails, as shown at 15 in FIG. 5. The guide rails 15 consist of two sets of rails, i.e., an upper set of rails and a lower set of rails. Each set of rails consist of an outer rail 15a and an inner rail 15b. The back cover of the camera contacts the outer rails 15a when it is closed. The film has its upper and lower edges held in contact with the inner rails 15b and travels in parallel to the outer rails 15a.
The known structure as hereinabove described has a number of disadvantages which are due to the fact that the shutter assembly 30 is fixed to the camera body 10 by the screws 36. This construction increases the distance L.sub.1 between the film plane and the shutter blade plane if the camera body 10 or the shutter assembly 30 is formed from a plastic material. This undesirably enlarges the camera and lowers its shutter efficiency.